RP215 monoclonal antibody described in U.S. Pat. No. 5,650,291 and PCT publication WO2008/138,139 is one of three thousand monoclonal antibodies which were generated in mice immunized against the extract of OC-3-VGH ovarian cancer cell. Through years of effort, it was documented that RP215 reacts specifically with cancer cell-expressed pan cancer biomarker or glycoproteins, designated as CA215. The amino acid sequence of the variable regions of RP215 is disclosed in the PCT publication. The contents of these documents as related to uses for antibodies that bind to CA215 are incorporated herein by reference.
Following comprehensive analysis of more than 100 CA215-derived tryptic peptides by MALDI-TOF MS, it was further demonstrated that CA215 is a mixture of glycoproteins expressed by cancer cells, each of which contains an RP215-specific carbohydrate-associated epitope. Among these glycoproteins are mainly immunoglobulin superfamily (IgSF) proteins including immunoglobulin heavy chains, T cell receptors and cell adhesion molecules as well as mucins and others.
Both in vitro and in vivo biochemical and immunological assays were performed to document that RP215 reacts with the surface of almost all of cancer cells or cancerous tissues in humans. Besides immunohistochemical studies, apoptosis as well as complement-dependent cytotoxicity can be induced to cancer cells in the presence of RP215 at concentrations on the order of μg/ml. Growth inhibition of implanted tumor cells in model systems by RP215 was also demonstrated in nude mouse experiments. In addition, rat anti-idiotypic (Aid) monoclonal antibodies against RP215 were generated. The Ab3 response upon immunizations of these Aid monoclonal antibodies in mice was successfully induced. The anti-aid (Ab3) anti-sera were shown to be functionally equivalent to RP215. Aid monoclonal antibodies may also be used for the development of anti-cancer vaccines for human applications.
To develop RP215-based anti-cancer drugs for human application, it is essential to modify the original murine RP215 monoclonal antibody into humanized form.